patch-O1int-0306281420 for 2.5.73 interactivity

[Con Kolivas <kernel@kolivas.org>]

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For my sins I've included what I thought was necessary for this patch. 

The interactivity for tasks is based on the sleep avg accumulated divided by 
the running time of the task. However since the accumulated time is not 
linear with time it now works on the premise that running time is an 
exponential function entirely. Pat Erley was the genius who implemented this 
simple exponential function in surprisingly low overhead integer maths.

Also added was some jiffy wrap logic (as if anyone would still be running my 
patch in 50 days :P).

Long sleepers were reclassified as idle according to the new exponential 
logic.

If you test, please note this works better at 1000Hz.

Attached also is my bastardised version of Ingo's timeslice granularity patch. 
This round robins tasks on the active array every 10ms, which _might_ be 
detrimental in throughput applications but has not been benchmarked. However 
for desktops it does wonders to smoothing out the jerkiness of X and I highly 
recommend using this in combination with the O1int patch.

This is very close to all the logic I wanted to implement. It might need more 
tuning... Note parent penalty, child penalty and exit weight (uppercase) no 
longer do anything.

Please test and comment.

Con

P.S. In the words of Zwane - there is always a corner case. Corner case I 
think I still need to tackle is the application that spins madly waiting for 
it's child to start, and in the process it is the parent that is starving the 
child by being higher priority than it. This seems to be a coding style 
anomaly brought out by the scheduler.
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diff -Naurp linux-2.5.73/include/linux/sched.h linux-2.5.73-test/include/linux/sched.h
--- linux-2.5.73/include/linux/sched.h	2003-06-26 01:30:42.000000000 +1000
+++ linux-2.5.73-test/include/linux/sched.h	2003-06-28 14:09:08.000000000 +1000
@@ -336,6 +336,7 @@ struct task_struct {
 	prio_array_t *array;
 
 	unsigned long sleep_avg;
+	unsigned long avg_start;
 	unsigned long last_run;
 
 	unsigned long policy;
diff -Naurp linux-2.5.73/kernel/fork.c linux-2.5.73-test/kernel/fork.c
--- linux-2.5.73/kernel/fork.c	2003-06-26 01:30:42.000000000 +1000
+++ linux-2.5.73-test/kernel/fork.c	2003-06-28 14:09:08.000000000 +1000
@@ -863,6 +863,7 @@ struct task_struct *copy_process(unsigne
 	p->array = NULL;
 	p->lock_depth = -1;		/* -1 = no lock */
 	p->start_time = get_jiffies_64();
+	p->avg_start = jiffies;
 	p->security = NULL;
 
 	retval = -ENOMEM;
diff -Naurp linux-2.5.73/kernel/sched.c linux-2.5.73-test/kernel/sched.c
--- linux-2.5.73/kernel/sched.c	2003-06-26 01:30:42.000000000 +1000
+++ linux-2.5.73-test/kernel/sched.c	2003-06-28 14:19:03.000000000 +1000
@@ -314,11 +314,29 @@ static inline void enqueue_task(struct t
 static int effective_prio(task_t *p)
 {
 	int bonus, prio;
+	long sleep_period, tau;
 
 	if (rt_task(p))
 		return p->prio;
 
-	bonus = MAX_USER_PRIO*PRIO_BONUS_RATIO*p->sleep_avg/MAX_SLEEP_AVG/100 -
+	tau = MAX_SLEEP_AVG;
+
+	sleep_period = jiffies - p->avg_start;
+	if (sleep_period > MAX_SLEEP_AVG)
+		sleep_period = MAX_SLEEP_AVG;
+	else if (!sleep_period)
+		return p->static_prio;
+	else {
+		sleep_period = (sleep_period *
+			17 * sleep_period / ((17 * sleep_period / (5 * tau) + 2) * 5 * tau));
+		if (!sleep_period)
+			return p->static_prio;
+	}
+
+	if (p->sleep_avg > sleep_period)
+		sleep_period = p->sleep_avg;
+
+	bonus = MAX_USER_PRIO*PRIO_BONUS_RATIO*p->sleep_avg/sleep_period/100 -
 			MAX_USER_PRIO*PRIO_BONUS_RATIO/100/2;
 
 	prio = p->static_prio - bonus;
@@ -349,8 +367,12 @@ static inline void activate_task(task_t 
 	long sleep_time = jiffies - p->last_run - 1;
 
 	if (sleep_time > 0) {
-		int sleep_avg;
 
+		if (sleep_time > HZ){
+			p->avg_start = jiffies - HZ;
+			p->sleep_avg = HZ / 13;
+		}
+		else {
 		/*
 		 * This code gives a bonus to interactive tasks.
 		 *
@@ -359,7 +381,7 @@ static inline void activate_task(task_t 
 		 * spends sleeping, the higher the average gets - and the
 		 * higher the priority boost gets as well.
 		 */
-		sleep_avg = p->sleep_avg + sleep_time;
+			p->sleep_avg += sleep_time;
 
 		/*
 		 * 'Overflow' bonus ticks go to the waker as well, so the
@@ -367,12 +389,14 @@ static inline void activate_task(task_t 
 		 * boosting tasks that are related to maximum-interactive
 		 * tasks.
 		 */
-		if (sleep_avg > MAX_SLEEP_AVG)
-			sleep_avg = MAX_SLEEP_AVG;
-		if (p->sleep_avg != sleep_avg) {
-			p->sleep_avg = sleep_avg;
-			p->prio = effective_prio(p);
+			if (p->sleep_avg > MAX_SLEEP_AVG)
+				p->sleep_avg = MAX_SLEEP_AVG;
+		}
+		if (unlikely((jiffies - MAX_SLEEP_AVG) < p->avg_start)){
+			p->avg_start = jiffies;
+			p->sleep_avg = 0;
 		}
+		p->prio = effective_prio(p);
 	}
 	__activate_task(p, rq);
 }
@@ -549,8 +573,6 @@ void wake_up_forked_process(task_t * p)
 	 * and children as well, to keep max-interactive tasks
 	 * from forking tasks that are max-interactive.
 	 */
-	current->sleep_avg = current->sleep_avg * PARENT_PENALTY / 100;
-	p->sleep_avg = p->sleep_avg * CHILD_PENALTY / 100;
 	p->prio = effective_prio(p);
 	set_task_cpu(p, smp_processor_id());
 
@@ -586,13 +608,6 @@ void sched_exit(task_t * p)
 			p->parent->time_slice = MAX_TIMESLICE;
 	}
 	local_irq_restore(flags);
-	/*
-	 * If the child was a (relative-) CPU hog then decrease
-	 * the sleep_avg of the parent as well.
-	 */
-	if (p->sleep_avg < p->parent->sleep_avg)
-		p->parent->sleep_avg = (p->parent->sleep_avg * EXIT_WEIGHT +
-			p->sleep_avg) / (EXIT_WEIGHT + 1);
 }
 
 /**

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diff -Naurp linux-2.5.73/kernel/sched.c linux-2.5.73-test/kernel/sched.c
--- linux-2.5.73/kernel/sched.c	2003-06-26 01:30:42.000000000 +1000
+++ linux-2.5.73-test/kernel/sched.c	2003-06-27 23:14:31.000000000 +1000
@@ -1229,7 +1229,16 @@ void scheduler_tick(int user_ticks, int 
 			enqueue_task(p, rq->expired);
 		} else
 			enqueue_task(p, rq->active);
+	} else {
+		if (!(p->time_slice % MIN_TIMESLICE) &&
+			       		(p->array == rq->active)) {
+			dequeue_task(p, rq->active);
+			set_tsk_need_resched(p);
+			p->prio = effective_prio(p);
+			enqueue_task(p, rq->active);
+		}
 	}
+
 out_unlock:
 	spin_unlock(&rq->lock);
 out: